SITE INFORMATION AND CORRESPONDENCE

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APPENDIX A: FIELD, SAMPLING, AND ANALYTICAL METHODS A.1: DRILLING During May 16 through 24,2005, SAIC observed Gregg Drilling(C57#485165)advance six soil borings (SB-22 through SB-25, SB-30, and SB-36) and install three monitoring wells (MW-5 through MW-7)as shown on Figure 2. Geoprobe and hollow-stem auger equipment were used to advance the proposed soil borings. During drilling activities, a continuous coring device was used to collect soil samples. The soil borings and monitoring wells were advanced to depths from 40 to 71.5 feet bgs. (The completion of soil borings and monitor wells generally conformed to SAIC Field Technical Procedure No. 525, "Soil Sampling Using an Auger.") Because previous investigations indicated the presence of residual petroleum in the soil to depths ranging from approximately 20 to 60 feet, soil borings were advanced to a target depth of 70 feet bgs. In accordance with the approach prescribed the Second Draft Revised Technical Approach to Site Evaluation and Decision Making, Old Valley Pipeline Sites, and to the extent practicable, SAIC attempted to collect soil samples from the target depth, or in the event of contamination, from the most affected soil interval (Geomatrix, 2005 update). The samples were screened using photoionization detection(PID)equipment,using procedures consistent with SAIC Field Technical Procedure No. 750,"Field Measurement Procedures—Organic Vapor Detection,"in order to detect the presence of residual petroleum in soil. The soil was logged in general accordance to the Unified Soil Classification System as presented in American Society for Testing and Materials 2488-90 under the supervision of a California Professional Geologist. Additionally,other information was entered into field logbooks to document where,when,how,and from whom any vital project information were obtained,using procedures described in SAIC FTP No. 1215, "Use of Field Logbooks." Following completion of the soil borings, each open borehole was either plugged and abandoned according to San Joaquin County Public Health Services(SJCPHS)and Stanislaus County Department of Environmental Resources (SCDER)requirements, or it was converted to a monitoring well. A.2: SOIL SAMPLING Soil samples from soil borings SB-22 through SB-25, SB-30, SB-36, and MW-5 were collected into EPA- approved containers and submitted to a California State-certified laboratory, Lancaster Laboratories (Lancaster)in Lancaster,Pennsylvania(ELAP#2501),under SAIC chain-of-custody protocols and analyzed for the constituents of concern(COCs): SAIC also collected soil samples from borings SB-22 through SB-25 and MW-5 for use in a future human health screening evaluation(HHSE). These soil samples were collected from 1 foot and 5 feet bgs. Soil samples collected for the HHSE were analyzed for COCs. However, so that soil samples were analyzed using detection limits sensitive(low) enough for the purposes of the HHSE, SAIC specified certain special detection limits. For more information,refer to Appendix C,Laboratory Data Evaluation and Laboratory Results. A.3: MONITORING WELL INSTALLATION SAIC installed groundwater monitoring wells MW-5 through MW-7,which have since been combined with existing monitoring wells MW-1 through MW-4 and incorporated into the quarterly monitoring and sampling program. A-1 From Science to Solutions-